The term "rubber", as used herein is intended to encompass all types of natural and synthetic rubber and various resilient materials that are composed of polymers, polymer components with other materials and polymer composites with material or synthetic rubber.
Tires for automotive vehicles are typically in the form of composites including layers of synthetic rubber, herein referred to as rubber, and layers of fabric and metal belting which provides the tires with structural integrity sufficient to significantly extend the service life thereof. The typical tire for passenger vehicles has an average weight in the order of twenty pounds including one pound of fabric belting, four pounds of steel belting and the remaining fifteen pounds being composed of synthetic rubber. The range of weight of typical passenger vehicle tires is in the order of from about twelve pounds to about twenty-six pounds. Vehicle tires are expendable items typically having a service life of from 30,000 miles to 60,000 miles. It is not unusual for a passenger automobile to be provided with from three to five sets of replacement tires during its service life.
In the past, when automotive tires have been removed and discarded they have been disposed of by burning or by depositing them in landfills. Obviously, synthetic rubber and the other constituents of vehicle tires do not break down in landfills even after many years. Thus, landfills which have accepted rubber tires for disposal have quickly become filled to capacity. Also, the increased costs of landfill type disposed facilities, and the various environmental problems that arise from landfill disposal operating have caused landfill disposal of this to be unsatisfactory and in many cases prohibited.
Another method for disposing of discarded vehicle tires is the practice of segregating them from conventional refuse and transporting them to a surface location for storage. The typical purpose of surface storage is to await the development of a process and apparatus for reclaiming the rubber and other materials from the tires so that the byproducts may be utilized in the manufacture of other articles or utilized as fuel such as for firing energy production plants. It is not unusual at the present time for a surface type tire storage facility to contain in the order from in excess of one million tires. These surface type storage facilities have a number of disadvantages that make them impractical. The tires in these facilities typically contain small volumes of rain water which becomes breeding areas for mosquitoes and other insects. Further, this retained water often becomes stagnant and can provide a developing environment for communicable diseases. At times these large volumes of stored discarded tires have become ignited by spontaneous combustion or by other means and have developed a fire and smoke hazard that is extremely difficult and expensive to combat. In general therefore, outdoor storage facilities for discarded tires presents a wide variety of problems that renders them unsuitable to the point that many government agencies have established deadlines for elimination of such tire storage areas.
More recently various companies, typically with governmental support, have initiated a number of differing processes for destruction of the fires and for reclamation of the byproducts thereof. Typically the tires are ground, shredded or chopped to a form where the rubber chunks or particles have a size range of about nine square inches. When tires are shredded the rubber chunks typically random in sizes from one square inch or greater. These chunks of rubber tire material typically incorporate synthetic rubber, steel and a polymer fabric. The chunk form rubber tire material is then transported via conveyer or by any other suitable means to a surface based storage facility. The resulting chopped, shredded or ground rubber tire material has been treated in a number of ways to render it to a satisfactory form for reuse. For example, processes have been developed for microwave revulcanization of the material and for its destruction and rendering to an energy form by means of pyrolysis.
Because the steel fibers and polymer fabric materials typically remain with the rubber shreds, these constituents are often detrimental to effective reclamation of the rubber for use in the manufacture of other articles. It is desirable therefore to provide a method and apparatus for reducing rubber tire material to a pulverulent form and which prepares the material for efficient separation of tire constituents such as steel fibers and polymer fabric from the rubber.
During processing of rubber tire material especially for purposes of reclaiming the rubber for use in the manufacture of other articles, heat build up in the rubber tire material can become detrimental to future use of the rubber. In the event the rubber tire material becomes excessively hot, which very easily results from tire crumbing operations, the heat build up in the material can cause a molecular structural change in the rubber, thus rendering it unsuitable for use in article manufacturing processes. In this case, the resulting crumb rubber may be suitable only for use as fuel such as for energy producing facilities. Typically however the shredded crumb rubber material must be transported to a facility for energy production from one of the many tire storage facilities that have been established. The transportation costs of the reclaimed rubber tire constituents is often detrimental to utilization of the material even for energy production. It is desirable therefore to provide a method and apparatus for reclaiming rubber and other materials from used tires which does not cause undesirable heat induced molecular change of the rubber to the point that it becomes unsuitable for product manufacturing processes. It is also desirable to provide a method and apparatus for processing tires, which can be located at or near a manufacturing facility to thus minimize transportation and manufacturing costs.